Unlike earlier versions of PowerDirector, in 10 the chapter thumbnail can be hidden in the menu designer using the blue distortion handles. They are in the corners inside the white resizing rectangle of the thumbnail.
You need to drag the blue handle in the upper right corner all the way to the upper left corner of the white rectangle.
Then drag the blue handle in the lower left corner all the way to the lower right corner of the white rectangle. You'll end up with a thin diagonal line going from the upper left to lower right corners of the white rectangle. It's kind of tricky. If you do it correctly, the thumbnail will be completely invisible.
Next you need to import your square or round button and place it inside the white resizing rectangle with the hidden thumbnail. You may have to move the white rectangle out of the way temporarily so you can move your button into position. The white rectangle can then be moved back and re-sized if necessary so it encloses your button and the text item that is associated with it.
Your button will fade in and out while the menu is played. To prevent it from fading in and out, you need to drag the left and right edges of the blue (static indicator) section of the keyframe bar so they cover the orangish-yellow (fade-in/fade-out) sections of the keyframe bar, just as in the PiP designer. The keyframe bar is that orange/blue/orange bar at the bottom of the menu designer.
Gateway DX4380, AMD A8-5500 Quad Core 3.2GHz with ATI Radeon HD 7560D; 16GB RAM; 1 TB SATA 7200 RPM; Windows 8 Pro 64-bit; PDR11, PDVD12.